(1) Field of the Invention
The invention relates to the fabrication of integrated circuit devices, and more particularly to the fabrication of wire bond pads over underlying active devices, passive devices and/or weak dielectric layers.
(2) Background of the Invention
Performance characteristics of semiconductor devices are typically improved by reducing device dimensions, resulting in increased device densities and increased device packaging densities. This increase in device density places increased requirements on the interconnection of semiconductor devices, which are addressed by the packaging of semiconductor devices. One of the key considerations in the package design is the accessibility of the semiconductor device or the Input/Output (I/O) capability of the package after one or more devices have been mounted in the package.
In a typical semiconductor device package, the semiconductor die can be mounted or positioned in the package and can further be connected to interconnect lines of the substrate by bond wires or solder bumps. For this purpose the semiconductor die is provided with pads (bond pads) that are, typically mounted around the perimeter of the die, and are located such as not to be formed over regions containing active or passive devices.
One reason the bond pads are not formed over the active or passive devices is related to the thermal and/or mechanical stresses that occur during the wire bonding process. During wirebonding, wires are connected from the bond pads to a supporting circuit board or to other means of interconnections.
The semiconductor industry has recently turned increasingly to low dielectric-constant (or low-k) materials for intermetal dielectrics. However, such materials typically have lower mechanical strength than traditional insulating materials and are thus also susceptible to damage by wire bonding.
U.S. Pat. No. 4,636,832 (Abe et al.) describes a method of forming a bond pad over an active area, using a silicon layer for stress reduction.
U.S. Pat. No. 5,751,065 (Chittipeddi et al.) discloses a method of providing an integrated circuit with active devices under the bond pads, and uses metal for stress relief.
U.S. Pat. No. 6,384,486 (Zuniga et al.) shows a method of forming an integrated circuit under a contact pad, also using a metal layer for stress absorption.
U.S. Pat. No. 6,229,221 (Kloen et al.) describes forming a wire bond to a bond pad formed over active devices, where the bond pad and passivation must have specified thickness and be substantially free from interruptions under the wire bonding region.